Approach to bottom dielectric isolation for vertical transport fin field effect transistors

ABSTRACT

A vertical transport fin field effect transistor (VT FinFET), including one or more vertical fins on a surface of a substrate, an L-shaped or U-shaped spacer trough on the substrate adjacent to at least one of the one or more vertical fins, and a gate dielectric layer on the sidewalls of the at least one of the one or more vertical fins and the L-shaped or U-shaped spacer trough.

BACKGROUND Technical Field

The present invention generally relates to formation of a bottom spacerthat is independent of vertical fin density, and more particularly toforming an insulating dielectric trough as a part of a bottom spacer.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and finFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the finFET can be an upright slab of thin approximatelyrectangular Si, commonly referred to as the fin with a gate on the fin,as compared to a MOSFET with a single gate in the plane of thesubstrate. Depending on the doping of the source and drain, an n-FET ora p-FET can be formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also can be coupled to form a complementary metaloxide semiconductor (CMOS) device, where a p-channel MOSFET andn-channel MOSFET are coupled together.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts become more difficult. An approach istherefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

In accordance with an embodiment of the present invention, a verticaltransport fin field effect transistor (VT FinFET), including one or morevertical fins on a surface of a substrate, an L-shaped or U-shapedspacer trough on the substrate adjacent to at least one of the one ormore vertical fins, and a gate dielectric layer on the sidewalls of theat least one of the one or more vertical fins and the L-shaped orU-shaped spacer trough is provided.

In accordance with another embodiment of the present invention, a methodof forming a vertical transport fin field effect transistor, including,forming one or more vertical fins on a substrate, forming a spacer layeron the substrate and exposed surfaces of the one or more vertical fins,forming a gauge layer on the spacer layer, removing a portion of thegauge layer to form one or more gauge sections on the spacer layer,where a portion of the spacer layer on the one or more vertical fins isexposed by removing the portion of the gauge layer, and removing theexposed portion of the spacer layer to form an L-shaped or U-shapedspacer trough is provided.

In accordance with yet another embodiment of the present invention, amethod of forming a vertical transport fin field effect transistor,including, forming one or more vertical fins on a substrate, forming aliner layer on the substrate and exposed surfaces of the one or morevertical fins, forming a spacer layer on at least a portion of the linerlayer, forming a gauge layer on the spacer layer, removing a portion ofthe gauge layer to form one or more gauge sections on the spacer layer,where a portion of the spacer layer on the one or more vertical fins isexposed by removing the portion of the gauge layer, removing the exposedportion of the spacer layer, wherein removing the exposed portion of thespacer layer exposes a portion of the underlying liner layer, andremoving the exposed portion of the underlying liner layer on the one ormore vertical fins is provided.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional side view showing a substrate, in accordancewith an embodiment of the present invention;

FIG. 2 is a cross-sectional side view showing a fin template layerformed on the surface of the substrate, a mandrel layer formed on thefin template layer, a mandrel template layer formed on the mandrellayer, and a mandrel mask layer formed on the mandrel template layer, inaccordance with an embodiment of the present invention;

FIG. 3 is a cross-sectional side view showing a patterned mandrel masklayer on the mandrel template layer, in accordance with an embodiment ofthe present invention;

FIG. 4 is a cross-sectional side view showing a patterned mandrel masklayer on the mandrel templates and sacrificial mandrels, in accordancewith an embodiment of the present invention;

FIG. 5 is a cross-sectional side view showing a sidewall layer formed onthe mandrel templates, sacrificial mandrels, and fin template layer, inaccordance with an embodiment of the present invention;

FIG. 6 is a cross-sectional side view showing sidewalls spacers formedon opposite sides of the sacrificial mandrels, in accordance with anembodiment of the present invention;

FIG. 7 is a cross-sectional side view showing sidewall spacers formed onthe fin template layer after removal of the sacrificial mandrels, inaccordance with an embodiment of the present invention;

FIG. 8 is a cross-sectional side view showing fin templates formed onthe substrate and sidewall spacers on each fin template, in accordancewith an embodiment of the present invention;

FIG. 9 is a cross-sectional side view showing a plurality of verticalfins formed on the substrate with a fin template and a sidewall spaceron each vertical fin, in accordance with an embodiment of the presentinvention;

FIG. 10 is a cross-sectional side view showing a fin template remainingon each tapered vertical fin after removal of the sidewall spacers, anda source/drain region below the vertical fins, in accordance with anembodiment of the present invention;

FIG. 11 is a cross-sectional side view showing a liner layer on thevertical fins fin templates, and substrate, in accordance with anembodiment of the present invention;

FIG. 12 is a cross-sectional side view showing a spacer layer on theliner layer over the vertical fins, fin templates, and substrate, inaccordance with an embodiment of the present invention;

FIG. 13 is a cross-sectional side view showing a gauge layer on thespacer layer and between the vertical fins, in accordance with anembodiment of the present invention;

FIG. 14 is a cross-sectional side view of the long axis of the verticalfins showing a gauge layer on the spacer layer, and an isolation regionbetween the vertical fins, in accordance with an embodiment of thepresent invention;

FIG. 15 is a cross-sectional side view showing the gauge layer with areduced height between the vertical fins, in accordance with anembodiment of the present invention;

FIG. 16 is a cross-sectional side view of the long axis of the verticalfins showing the gauge layer with a reduced height between the verticalfins, in accordance with an embodiment of the present invention;

FIG. 17 is a cross-sectional side view showing the spacer layer trimmedto the height of the gauge layer to produce a spacer trough, inaccordance with an embodiment of the present invention;

FIG. 18 is a cross-sectional side view showing the L-shaped and U-shapedspacer troughs on the liner layer after removal of a remaining portionof the gauge layer, in accordance with an embodiment of the presentinvention;

FIG. 19 is a cross-sectional side view of the long axis of the verticalfins showing the spacer troughs on the end walls of the vertical fins,and the remaining portion of the gauge layer in the isolation regionbetween the vertical fins, in accordance with an embodiment of thepresent invention;

FIG. 20 is a cross-sectional side view showing removal of the exposedportions of the liner layer from each vertical fin and fin template, inaccordance with an embodiment of the present invention;

FIG. 21 is a cross-sectional side view showing a gate dielectric layerformed on the vertical fins, fin templates, and exposed surfaces of thespacer trough, in accordance with an embodiment of the presentinvention;

FIG. 22 is a cross-sectional side view showing a work function layer onthe gate dielectric layer, in accordance with an embodiment of thepresent invention;

FIG. 23 is a cross-sectional side view showing a gate fill layer on thework function layer, in accordance with an embodiment of the presentinvention;

FIG. 24 is a cross-sectional side view showing gate structures formed onthe vertical fins, and a top spacer formed on the exposed portions ofthe gate structure, in accordance with an embodiment of the presentinvention;

FIG. 25 is a cross-sectional side view showing top source/drains andsource/drain contacts on the top surface of each vertical fin, inaccordance with an embodiment of the present invention; and

FIG. 26 is a cross-sectional side view of the long axis of the verticalfins showing the vertical fins, gate structures, source/drains, andelectrical contacts for an nFET and an adjacent pFET, in accordance withan embodiment of the present invention.

DETAILED DESCRIPTION

Principles and embodiments of the present invention relate generally toforming bottom spacers having a more uniform thickness between verticalfins that may vary in pitch and fin pattern density. The bottom spacercan include two layers formed in a manner that does not vary with thedistance between adjacent vertical fins. In various embodiments, anoxide liner layer and a nitride spacer layer can be formed on asubstrate and vertical fin(s) by thermal atomic layer deposition(Thermal ALD) or plasma enhanced atomic layer deposition (PEALD) toprovide a bottom spacer for a vertical transport field effect transistor(VTFET), where the current flows through the FinFET perpendicularly tothe plane of the substrate.

Principles and embodiments of the present invention also relatesgenerally to a U-shaped or L-shaped spacer trough that is conformallydeposited on the substrate and vertical fins to have a predeterminedthickness that is insensitive to trench width (i.e., inter-fin distance)and geometry. The conformal deposition can reduce or avoid thicknessvariations, where variability in bottom spacer thickness amongneighboring devices can induce device performance variations andinstabilities. For example, high density plasma deposited bottom spacerfilms can vary in thickness by as much as 10%-50% (e.g., about 1 nm toabout 4 nm) depending on the degree of pitch variation, shape of fillgeometry, re-entrancy, and deposition parameters.

Principles and embodiments of the present invention also relategenerally to use of conformal depositions by Thermal ALD or PEALD inplace of directional depositions, such as high density plasma (HDP)depositions, Physical Vapor Deposition (PVD), or gas cluster ion beam(GCIB) depositions, to better control the thickness of the layersthrough monolayer-by-monolayer layer formation. The deposition of aliner layer and a spacer layer by Thermal ALD and/or PEALD can avoidthickness variations due to pitch walking and vertical fin loading(Isolated vs. dense), where variations in fin pitch can cause localdepletion of layer forming reactants in denser areas, thereby resultingin different amounts of spacer and liner layer deposition thicknessesespecially for the PECVD or HDP processes.

In addition, Thermal ALD and PEALD deposited nitride layers can bepotentially achieved at lower thermal budgets, where the ALD or PEALDdeposition may be carried out at less than 500° C. Lower thermal budgetscan avoid dopant diffusion.

Exemplary applications/uses to which the present invention can beapplied include, but are not limited to: logic (e.g., NAND, NOR, XOR,etc.) and memory devices (e.g., SRAM, DRAM, etc.) utilizing verticaltransport FinFET devices.

In various embodiments, the materials and layers can be deposited byphysical vapor deposition (PVD), chemical vapor deposition (CVD), atomiclayer deposition (ALD), molecular beam epitaxy (MBE), or any of thevarious modifications thereof, for example, plasma-enhanced chemicalvapor deposition (PECVD), metal-organic chemical vapor deposition(MOCVD), low pressure chemical vapor deposition (LPCVD), electron-beamphysical vapor deposition (EB-PVD), and plasma-enhanced atomic layerdeposition (PEALD). The depositions can be epitaxial processes, and thedeposited material can be crystalline. In various embodiments, formationof a layer can be by one or more deposition processes, where, forexample, a conformal layer may be formed by a first process (e.g.,Thermal ALD, PEALD, etc.) and a fill may be formed by a second process(e.g., CVD, electrodeposition, PVD, etc.).

It is to be understood that the present invention will be described interms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of the present invention.

It should be noted that certain features may not be shown in all figuresfor the sake of clarity. This is not intended to be interpreted as alimitation of any particular embodiment, or illustration, or scope ofthe claims.

Reference to source/drain projections, layers, regions, etc., isintended to indicate that the particular device feature can beimplemented as a source or a drain except as expressly indicatedotherwise. In addition, the role of source and drain for an activedevice can in some instances be reversed, so a previously indicateddrain may instead be a source and vice versa. Reference to asource/drain is, therefore, intended to encompass the broadestreasonable scope of the term.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a cross-sectional side viewof a substrate is shown, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a substrate 110 can be a semiconductor or aninsulator with an active surface semiconductor layer. The substrate caninclude crystalline, semi-crystalline, microcrystalline, or amorphousregions. The substrate can be essentially (i.e., except forcontaminants) a single element (e.g., silicon), primarily (i.e., withdoping) of a single element, for example, silicon (Si) or germanium(Ge), or the substrate can include a compound, for example, Al₂O₃, SiO₂,GaAs, SiC, or SiGe. The substrate can also have multiple materiallayers, for example, a semiconductor-on-insulator substrate (SeOI), suchas a silicon-on-insulator substrate (SOI), germanium-on-insulatorsubstrate (GeOI), or silicon-germanium-on-insulator substrate (SGOI).The substrate can also have other layers forming the substrate,including high-k oxides and/or nitrides. The substrate 110 can include acarrier layer to support thinner layers.

In one or more embodiments, the substrate 110 can be a silicon wafer. Invarious embodiments, the substrate can be a single crystal silicon (Si),silicon-germanium (SiGe), or III-V semiconductor (e.g., GaAs) wafer, orhave a single crystal silicon (Si), silicon-germanium (SiGe), or III-Vsemiconductor (e.g., GaAs) surface/active layer.

FIG. 2 is a cross-sectional side view showing a fin template layerformed on the surface of the substrate, a mandrel layer formed on thefin template layer, a mandrel template layer formed on the mandrellayer, and a mandrel mask layer formed on the mandrel template layer, inaccordance with an embodiment of the present invention

In one or more embodiments, a fin template layer 120 can be formed on atleast a portion of a surface of a substrate 110. In various embodiments,the fin template layer 120 can be formed on the substrate surface byCVD, PECVD, PVD, thermal growth, or combinations thereof, where the fintemplate layer 120 can be blanket deposited on the substrate.

In one or more embodiments, the fin template layer 120 can have athickness in the range of about 20 nm to about 70 nm, or in the range ofabout 20 nm to about 50 nm, or in the range of about 50 nm to about 70nm, or in the range of about 30 nm to about 60 nm, where the thicknessof the fin template layer 120 can define the height of subsequentlyformed source/drain projections. Other thicknesses are alsocontemplated.

In various embodiments, a fin template layer 120 can be a hard masklayer for masking the substrate during transfer of a vertical finpattern to the substrate 110. The fin template layer 120 can be siliconoxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), siliconcarbonitride (SiCN), silicon boronitride (SiBN), silicon carbide (SiC),silicon borocarbide (SiBC), silicon boro carbonitride (SiBCN), boroncarbide (BC), boron nitride (BN), titanium nitride (TiN), orcombinations thereof, where the fin template layer 120 may include oneor more layers. The fin template layer 120 can also act as an etch-stoplayer for forming sacrificial mandrels from a mandrel layer, where thefin template layer 120 can be selectively etched relative to otherlayers.

In one or more embodiments, a mandrel layer 130 can be formed on atleast a portion of the fin template layer 120. In one or moreembodiments, the mandrel layer 130 can be formed by CVD, PECVD, PVD, aspin-on process, or combinations thereof, where the mandrel layer 130can be blanket deposited on the fin template layer 120.

In various embodiments, mandrel layer 130 can be a sacrificial materialthat can be easily and selectively patterned and etched. The mandrellayer 130 can be amorphous silicon (a-Si), poly-silicon (p-Si),amorphous carbon (a-C), silicon-germanium (SiGe), an organicplanarization layer (OPL), silicon oxide (SiO), silicon nitride (SiN),or suitable combinations thereof.

In one or more embodiments, a mandrel template layer 140 can be formedon the mandrel layer 130, where the mandrel template layer can be a hardmask layer.

The mandrel template layer 140 can be a silicon oxide (SiO), a siliconnitride (SiN), a silicon oxynitride (SiON), a silicon carbonitride(SiCN), a silicon boronitride (SiBN), a silicon borocarbide (SiBC), asilicon boro carbonitride (SiBCN), a boron carbide (BC), a boron nitride(BN), or combinations thereof, where the mandrel template layer 140 mayinclude one or more layers.

In one or more embodiments, a mandrel mask layer 150 can be formed onthe mandrel template layer 140, where the mandrel mask layer 150 can bea hard mask layer or soft mask layer for masking the mandrel templatelayer 140. In one or more embodiments, the mandrel mask layer 150 can bea lithographic resist material (e.g., a photo resist material, an e-beamresist material, etc.).

In one or more embodiments, the mandrel mask layer 150 can be a positiveor negative resist material, for example, Poly(methyl methacrylate)(PMMA) or SU-8, or an electron-beam (e-beam) cured material, forexample, hydrogen silsesquioxane (HSQ).

In one or more embodiments, the mandrel mask layer 150 can be formed onthe mandrel template layer 140 by a spin on process.

FIG. 3 is a cross-sectional side view showing a patterned mandrel masklayer on the mandrel template layer, in accordance with an embodiment ofthe present invention.

In one or more embodiments, the mandrel mask layer 150 can be patternedand developed to form mandrel mask segments 151 on the mandrel templatelayer 140, where the mandrel mask segments 151 cover portions of themandrel template layer 140 and expose other portions of the mandreltemplate layer. The mandrel mask layer 150 can be patterned anddeveloped using processes known in the art.

In various embodiments, the pitch (i.e., center-to-center distance)between adjacent mandrel mask segments 151 can be in the range of about20 nm to about 60 nm, or in the range of about 20 nm to about 40 nm,which can determine the pitch between vertical fins.

FIG. 4 is a cross-sectional side view showing a patterned mandrel masklayer on the mandrel templates and sacrificial mandrels, in accordancewith an embodiment of the present invention.

In one or more embodiments, the exposed portions of the mandrel templatelayer 140 can be removed by wet etching or by a dry plasma etch, wherethe dry plasma can be a directional reactive ion etch (RIE). Removal ofthe exposed portions of the mandrel template layer 140 can form one ormore mandrel templates 141 below the mandrel mask segments 151, andexpose underlying portions of the mandrel layer 130. The mandreltemplates 141 can be used to transfer the mandrel pattern to the mandrellayer 130.

In one or more embodiments, once the mandrel templates 141 are formed, adirectional etch (e.g., RIE) can be used to remove exposed portions ofthe mandrel layer 130 to form sacrificial mandrels 131 on the underlyingfin template layer 120. The one or more sacrificial mandrels 131 can beon the fin template layer 120, where portions of the fin template layercan be exposed between the sacrificial mandrel(s) 131.

FIG. 5 is a cross-sectional side view showing a sidewall layer formed onthe mandrel templates, sacrificial mandrels, and fin template layer, inaccordance with an embodiment of the present invention.

In one or more embodiments, the mandrel mask segments 151 can be removedto expose the mandrel templates 141 using a process known in the art(e.g., stripping or ashing).

In one or more embodiments, a sidewall spacer layer 160 can be formed onthe exposed surfaces of the mandrel templates 141 and sacrificialmandrels 131, where the sidewall spacer layer 160 can be formed by aconformal deposition, for example, Thermal ALD or PEALD, to control thethickness of the sidewall spacer layer 160.

In various embodiments, the sidewall spacer layer 160 can have athickness in the range of about 4 nm to about 30 nm, or in the range ofabout 6 nm to about 15 nm, or in the range of about 8 nm to about 12 nm,where the thickness of the sidewall spacer layer 160 can determine thepitch and/or width of subsequently formed vertical fins.

In various embodiments, the sidewall spacer layer 160 can be siliconoxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), siliconcarbide (SiC), conformal amorphous carbon (a-C), or combinationsthereof.

FIG. 6 is a cross-sectional side view showing sidewalls spacers formedon opposite sides of the sacrificial mandrels, in accordance with anembodiment of the present invention.

In one or more embodiments, a portion of the sidewall spacer layer 160on the fin template layer 120 and the top surfaces of the mandreltemplates 141 can be removed by an etch-back process using a directionaletch, for example, RIE to remove the portion of the sidewall spacerlayer on surfaces approximately perpendicular to the incident ion beam,while the sidewall spacer layer 160 on the vertical sidewalls of thesacrificial mandrels 131 remain essentially unetched. In one or moreembodiments, a portion of the sidewall spacer layer 160 on the topsurfaces of the mandrel templates 141 can be removed by achemical-mechanical polishing (CMP) to expose the underlying mandreltemplates 141. The remaining portion of the sidewall spacer layer 160 onthe sacrificial mandrels 131 can form sidewall spacers 161.

In various embodiments, a plurality of vertical fins can be formed by asidewall image transfer (SIT) process, self-aligned double patterning(SADP), or self-aligned quadruple patterning (SAQP) to provide a tightpitch between vertical fins. In various embodiments, a direct print canbe used to provide fins with a looser pitch. Immersion Lithography candirect print down to about 78 nm pitch. Self-aligned double patterning(SADP) can achieve down to about 40 nm to 60 nm fin pitch. Self-alignedquadruple patterning (SAQP) may be used to go down to below 40 nm finpitch.

FIG. 7 is a cross-sectional side view showing sidewall spacers formed onthe fin template layer after removal of the sacrificial mandrels, inaccordance with an embodiment of the present invention.

In one or more embodiments, the mandrel templates 141 and sacrificialmandrels 131 can be removed after the sidewalls spacers 161 are formed,where the mandrel templates 141 and sacrificial mandrels 131 can beremoved by selective etching (e.g., RIE or wet etch). The mandreltemplates 141 and sacrificial mandrels 131 can be selectively removed,while the sidewalls spacers 161 remain on the fin template layer 120forming a fin pattern. The sidewalls spacers 161 can be made of adifferent material from the mandrel templates 141 and sacrificialmandrels 131, so the mandrel templates 141 and sacrificial mandrels 131can be selectively removed.

FIG. 8 is a cross-sectional side view showing fin templates formed onthe substrate and sidewall spacers on each fin template, in accordancewith an embodiment of the present invention;

In one or more embodiments, the fin pattern formed by the sidewallsspacers 161 can be transferred to the fin template layer 120 by removingthe exposed portion of the fin template layer 120. In variousembodiments, a portion of the fin template layer 120 can be removed toform a fin template 121 below each of the one or more sidewall spacers161 by a directional RIE. Removal of the portions of the fin templatelayer 120 can expose portions of the underlying substrate 110,surface/active layer(s), or source/drain layer(s) between each of thesidewall spacers 161 and fin templates 121.

FIG. 9 is a cross-sectional side view showing a plurality of verticalfins formed on the substrate with a fin template and a sidewall spaceron each vertical fin, in accordance with an embodiment of the presentinvention.

In one or more embodiments, one or more vertical fin(s) 111 can beformed on the substrate 110 or a surface active layer, where thevertical fin(s) 111 can be formed by removing a portion of the substrate110 between and/or around a sidewall spacer 161 and fin template 121.The one or more vertical fin(s) 111 can be formed by a directional etch,for example, a reactive ion etch (RIE) that removes the portion of thesubstrate or surface active layer not covered by a sidewall spacer 161.The removal of the substrate material can form vertical fin(s) 111 witha tapered profile having a greater width at the base of the verticalfin(s) and a narrower width at the top of the fin(s), or with a straightprofile (i.e., an essentially uniform width), where the straight ortapered profile can be produced as an aspect of the etching process.

In one or more embodiments, trenches can be formed in the substrate orsurface active layer between and/or around a sidewall spacer 161 and fintemplate 121 to a depth, Di, in the range of about 30 nm to about 90 nm,or in the range of about 30 nm to about 50 nm, or about 45 nm, where thevertical fin(s) 111 formed in the substrate can have a resulting height,H₁, equal to the depth of the trench. The vertical fin(s) 111 can have atapered profile with a width at the base greater than the width of thesidewall spacer 161 and fin template 121 on the top surface 113.

In non-limiting exemplary embodiments, the substrate 110 can be a singlecrystal silicon (Si) wafer or a single crystal silicon-germanium(Si_(x)Ge_(y)) wafer, or the substrate can include a single crystalsilicon (Si) or single crystal silicon-germanium active layer(Si_(x)Ge_(y)) at the surface of the substrate 110 (i.e., surface activelayer) from which a plurality of vertical fins can be formed. Thevertical fins 111 can be undoped to provide fully depleted devicechannels.

In one or more embodiments, the vertical fin(s) 111 can have a length inthe range of about 20 nm to about 60 nm, or about 30 nm to about 50 nm,where the vertical fin length can be equal to or greater than the width,W₁. The vertical fin(s) 111 can have a substantially (e.g., with roundededges and rough/uneven surfaces) square or rectangular cross-sectionparallel with the plane of the substrate 110.

In one or more embodiments, the vertical fins(s) 111 can be strained orunstrained fin(s), for example, a strained Si_(x)Ge_((1-x))nFET and/oran unstrained silicon pFET, or a III-V nFET to provide high carriermobility. The vertical fin(s) 111 on the substrate may be used tofabricate one or more vertical transport fin field effect transistors(VT FinFETs). The VT FinFETs may be electrically coupled to form CMOSdevices, where an nFET and a pFET are coupled to form the CMOS device.

FIG. 10 is a cross-sectional side view showing a fin template remainingon each tapered vertical fin after removal of the sidewall spacers, anda source/drain region below the vertical fins, in accordance with anembodiment of the present invention.

In one or more embodiments, the sidewall spacers 161 can be removed fromthe fin templates 121 and vertical fins 111. The vertical fins 111 canhave tapered sidewall profiles, where the base 112 of a vertical fin 111has a greater width, W₂, than the width, W₁, at the top surface 113 ofthe vertical fin 111. The sidewall spacers 161 can be removed, forexample, by an isotropic dry etch, a selective RIE process, or aselective wet etch. The underlying fin template(s) 121 can act as anetch stop. The fin template(s) 121 can remain on the vertical fin(s) 111after the sidewall spacers 161 are removed, and be subsequently removedby a separate selective etch.

In one or more embodiments, the width, W₁, at the top surface 113 of thevertical fin can be in the range of 6 nm to about 10 nm, and the width,W₂, at the base 112 of the vertical fin can be about 2 nm to about 4 nmwider than the width, W₁.

In one or more embodiments, the vertical fins 111 can have a pitch orcenter-to-center distance, P₁, P₂, determined by the pitch and width ofthe sacrificial mandrels 131. In various embodiments, the vertical fins111 can have a pitch, P₁, as determined by the width of the sacrificialmandrels 131 in the range of about 20 nm to about 60 nm, or in the rangeof about 30 nm to about 40 nm. In various embodiments, the vertical fins111 can have a pitch, P₂, as determined by the pitch between twoadjacent sacrificial mandrels 131 in the range of about 20 nm to about100 nm, or in the range of about 30 nm to about 90 nm, or in the rangeof about 40 nm to about 70 nm, where the pitch, P₁, can be equal to thepitch, P₂. In various embodiments, the pitch, P₁, and the pitch, P₂, canbe equal, or P₁ and P₂ can be different, where the difference can be dueto pitch walking. The present approach can provide a uniform thicknessto a bottom spacer when there are different/variable pitches betweenneighboring vertical fins 111.

In one or more embodiments, a bottom source/drain region 115 can beformed at the surface of the substrate, where the bottom source/drainregion 115 can be formed by implantation of an n-type or p-type dopingspecies, by epitaxially growing a doping layer on the surface of thesubstrate and vertical fin(s) 111, or a combination thereof. The bottomsource/drain can be a combination of both an epitaxial doping layer anddopant implantation to achieve a higher dopant density than thatachievable by either alone. The doping layer can be epitaxially grownbefore or after vertical fin patterning. The implantation and/orepitaxially grown doping layer can be followed by one or more anneals toallow dopants to diffuse laterally into the region below each of thevertical fin(s) 111. The doping species may also diffuse into a lowerportion of the vertical fin(s) 111 to form extension regions 116 at thebase 112 of a vertical fin 111. The bottom junction for the bottomsource/drain can be formed prior to forming a bottom spacer, but afterforming the vertical fin(s) 111. Other suitable doping techniques mayalso be used, including but not limited to, gas phase doping, plasmadoping, plasma immersion ion implantation, cluster doping, infusiondoping, liquid phase doping, solid phase doping, or combinationsthereof.

FIG. 11 is a cross-sectional side view showing a liner layer on thevertical fins fin templates, and substrate, in accordance with anembodiment of the present invention.

In one or more embodiments, a liner layer 170 can be formed on theexposed surfaces of the vertical fin(s) 111 and exposed surface of thesubstrate 110, where the liner layer 170 can be formed by a conformaldeposition on the vertical fin(s) 111 by Thermal ALD, PEALD, pulsedplasma CVD, or combinations thereof. In various embodiments, the linerlayer 170 is not formed by a directional deposition, including, but notlimited to, high density plasma (HDP) depositions and gas cluster ionbeam (GCIB) depositions. In various embodiments, the liner layer 170 isnot formed by CVD, LPCVD, or PECVD.

In one or more embodiments, the liner layer 170 can be a silicon oxide(SiO), a carbon-doped silicon oxide (SiOC), or combinations thereof. Asilicon oxide can include stoichiometric silicon dioxide (SiO₂) andother stoichiometric ratios of silicon and oxygen.

In one or more embodiments, the liner layer 170 can have a thickness inthe range of about 0.5 nm to about 10 nm, or in the range of about 0.5nm to about 5 nm, or about 1 nm to about 5 nm, or about 1 nm to about 3nm, although other thicknesses are contemplated.

FIG. 12 is a cross-sectional side view showing a spacer layer on theliner layer over the vertical fins fin templates, and substrate, inaccordance with an embodiment of the present invention.

In one or more embodiments, a spacer layer 180 can be formed on theliner layer 170 over the vertical fin(s) 111 and substrate 110, wherethe spacer layer 180 can be formed by a conformal deposition on thevertical fin(s) 111 by Thermal ALD, PEALD, pulsed plasma CVD, orcombinations thereof. In various embodiments, the spacer layer 180 isnot formed by a directional deposition, including, but not limited to,high density plasma (HDP) depositions and gas cluster ion beam (GCIB)depositions. In various embodiments, the spacer layer 180 is not formedby PECVD.

In one or more embodiments, the spacer layer 180 can be a siliconnitride (SiN), a carbon-doped silicon nitride (SiCN), a siliconoxynitride (SiON), silicon boro carbonitride (SiBCN), siliconoxycarbonitride (SiOCN), or combinations thereof. The silicon nitridecan include stoichiometric silicon nitride (Si₃N₄) and otherstoichiometric ratios of silicon and nitrogen.

In one or more embodiments, the spacer layer 180 can have a thickness inthe range of about 0.5 nm to about 10 nm, or in the range of about 0.5nm to about 5 nm, or about 1 nm to about 5 nm, or about 3 nm to about 8nm, although other thicknesses are contemplated.

In one or more embodiments, the vertical fins 111 can be a crystallinesemiconductor with a predetermined crystal orientation, where removal ofthe one or more exposed fin templates 121 exposes a crystalline surface.

FIG. 13 is a cross-sectional side view showing a gauge layer on thespacer layer and between the vertical fins, in accordance with anembodiment of the present invention.

In one or more embodiments, a gauge layer 190 can be formed on theexposed surfaces of the spacer layer 180, where the gauge layer 190 canbe formed by a blanket deposition, for example, flowable CVD (e.g.,SiO₂), eHARP, a spin-on process, or a combination thereof.

In one or more embodiments, the gauge layer 190 can be silicon dioxide(SiO₂), a low-k dielectric, a flowable polymeric material, or acombination thereof. A low-k dielelctric material can include, but notbe limited to, carbon-doped silicon oxide (SiOC), a fluoride-dopedsilicon oxide (e.g., fluoride doped glass), amorphous carbon, a poroussilicon oxide, a spin-on silicon based polymeric material (e.g.,tetraethyl orthosilicate (TEOS), hydrogen silsesquioxane (HSQ) andmethylsilsesquioxane (MSQ)), or combinations thereof.

FIG. 14 is a cross-sectional side view of the long axis of the verticalfins showing a gauge layer on the spacer layer, and an isolation regionbetween the vertical fins, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the portion of the gauge layer 190 extendingabove the top surface of the spacer layer 180 on the fin templates 121can be removed, for example, by a chemical-mechanical polishing (CMP) toprovide a smooth, planarized surface to the gauge layer 190. The topsurfaces of the spacer layer 180 on the fin templates 121 can be exposedby removal of the upper portion of the gauge layer 190.

In one or more embodiments, the gauge layer 190 can fill in an isolationregion trench to form an isolation region 195 (e.g., a shallow trenchisolation region) between two vertical fins 111. The isolation regiontrench can be lined with the liner layer 170 and spacer layer 180. Invarious embodiments, a first vertical fin 111 can be configured to be ann-type FinFET, and a second vertical fin 111 adjacent to the firstvertical fin 111 can be configured to be a p-type FinFET, where thebottom source/drain region 115 below the first vertical fin 111 andextension region 116 can be suitably doped to form an n-type FinFET(shown as left-diagonal hatching), and the bottom source/drain region115 below the second vertical fin 111 and extension region 116 can besuitably doped to form a p-type FinFET (shown as right-diagonalhatching). The isolation region 195 can physically and electricallyseparate bottom source/drain region 115 below the first vertical fin 111and the bottom source/drain region 115 below the second vertical fin111, such that the n-type FinFET and p-type FinFET are electricallyisolated. A portion of the vertical fins 111 forming the n-type FinFETand p-type FinFET can be undoped to provide a fully depleted devicechannel.

FIG. 15 is a cross-sectional side view showing the gauge layer with areduced height between the vertical fins, in accordance with anembodiment of the present invention.

In one or more embodiments, a portion of the gauge layer 190 can beremoved to form gauge sections 191 on the spacer layer 180 betweenand/or around vertical fin(s) 111, where the gauge sections 191 cancover the portions of the spacer layer 180 between vertical fins 111.The portion of the gauge layer 190 removed can reduce the height (i.e.,thickness) of the gauge layer 190 to a predetermined value for theintended depth of a U-shaped spacer trough, or L-shaped spacer troughwhere the spacer layer has a fin along only one side, formed from thespacer layer 180. The sidewalls 182 of the spacer trough 181 can have aninside height equal to the thickness of the gauge section 191. Invarious embodiments, the height of the leg of the spacer trough up theside of the vertical fin 111 can depend of the intended channel lengthof the FinFET.

In various embodiments, the height of the extension region 116 from thebase 112 of the vertical fin 111 can be equal to the height of the legof the spacer trough up the side of the vertical fin 111 to minimizeresistance and provide a predetermined channel length.

In one or more embodiments, the portion of the gauge layer 190 can beremoved using a selective, isotropic etch (e.g., wet etch, dry etch,such as COR, a remote plasma etch (e.g., SiCoNi™), etc.) thatpreferentially removes the material of the gauge layer 190, whileleaving the spacer layer 180 on the liner layer 170 covering thesidewalls of the vertical fin(s) 111 and the fin templates 121. The etchprocess can also be a directional etch, for example, reactive ion etch(RIE) that preferentially removes the material of the gauge layer 190.The etch can be a timed etch to remove a predetermined amount of thegauge layer 190, or it could be a combination of a wet etch, isotropicdry etch, and/or directional etch (e.g., RIE) in various sequences.

In one or more embodiments, the gauge section 191 can have a height(i.e., thickness) in the range of about 1 nm to about 6 nm, or in therange of about 1 nm to about 5 nm, or in the range of about 1 nm toabout 4 nm.

In one or more embodiments, the height of the gauge layer 190 can bereduced to expose the spacer layer 180 on the upper portion of thevertical fin(s) 111. The gauge layer 190 can be recessed below theheight of the vertical fin(s) 111.

FIG. 16 is a cross-sectional side view of the long axis of the verticalfins showing the gauge layer with a reduced height between the verticalfins, in accordance with an embodiment of the present invention.

In one or more embodiments, the height of the gauge layer 190 can bereduced to expose the spacer layer 180 on the upper portion of thevertical fin(s) 111, while covering a lower portion of the spacer layer180. The gauge layer 190 can be recessed to a predetermined height abovethe base 112 of the vertical fin(s) 111. The material of the gauge layer190 remains in the isolation region 195 between the two adjacent fins,where one fin can form a pFET and the other fin can form an nFET.

FIG. 17 is a cross-sectional side view showing the spacer layer trimmedto the height of the gauge layer to produce a spacer trough, inaccordance with an embodiment of the present invention.

In one or more embodiments, the exposed portion of the spacer layer 180can be removed using an isotropic etch (e.g., wet etch, dry isotropicetch, such as, SiCoNi™ etch, or chemical oxide removal (COR) etch, etc.)selective for the material of the spacer layer 180 to form a U-shapedspacer trough 181 between two vertical fins 111, or an L-shaped spacertrough 181 adjacent to a single vertical fin 111. The exposed portion ofthe spacer layer 180 can be removed down to the exposed top surface ofthe gauge section 191, where the remaining portion of the spacer layer180 on the vertical fin(s) 111 forms the sidewall(s) 182 of the spacertrough 181. Trimming the spacer layer 180 down to the top surface of thegauge section 191 exposes a portion of the liner layer 170 on thevertical fin(s) 111 and fin template(s) 121. The liner layer 170 can bea different material from the spacer layer 180, so the liner layer actsas an etch stop. The liner layer 170 can protect the fin template(s) 121which can be the same material as the spacer layer 180 to provide acontrolled sequence of etching processes to produce the troughs.

In a non-limiting exemplary embodiment, a silicon dioxide (SiO₂) linerlayer 170 can be formed on the vertical fin(s) 111 and fin templates 121by PEALD, and a silicon nitride (Si₃N₄) spacer layer 180 can be formedon the liner layer 170 by ALD. A flowable silicon oxide (SiO) can beformed by Flowable Chemical Vapor Deposition (FCVD) on the spacer layer180 and in the gaps between the vertical fins 111 to provide the gaugelayer 190. The fin templates 121 can be silicon nitride (Si₃N₄).

In various embodiments, the gauge layer 190 can be formed by High AspectRatio Process (HARP), enhanced High Aspect Ratio Process (eHARP), orhigh density plasma (HDP). The gauge layer 190 can be cured usingultraviolet (UV) light or ozone (O₃), and steam annealed at atemperature in the range of 300° C. to 700° C. to stabilize the layerstructure by converting silazane oligomers (—Si—N—Si—) into Si—O—Si toprovide a stronger/denser gauge layer 190. A chemical-mechanicalpolishing (CMP) can be utilized to remove an upper portion and planarizethe gauge layer 190. Additionally, selective RIE can be used to removethe upper portion of the SiO gauge layer 190 relative to the siliconnitride (Si₃N₄) spacer layer 180 to form the gauge sections 191. Theexposed Si₃N₄ spacer layer 180 can be trimmed down to the top surface ofthe gauge section 191 using a selective isotropic etch, for example, ahot phosphoric acid etch, or dry isotropic etch such as “Frontier”™,where the silicon dioxide (SiO₂) liner layer 170 prevents removal ordamage to the fin template(s) 121 and vertical fin(s) 111. The remainingflowable silicon oxide (SiO) gauge sections 191 can be removed by aselective, directional etch (e.g., RIE) to expose the U-shaped orL-shaped spacer trough(s) 181.

FIG. 18 is a cross-sectional side view showing the L-shaped and U-shapedspacer troughs on the liner layer after removal of a remaining portionof the gauge layer, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the gauge section(s) 191 can be removed toexpose the underlying U-shaped or L-shaped spacer trough(s) 181, wherethe gauge section(s) 191 can be removed using a selective etch (e.g.,wet etch, dry etch, plasma etch, etc.). Removal of the gauge section(s)191 can leave the sidewalls 182 of the spacer trough(s) 181 extendingobliquely or perpendicularly up a portion of a vertical fin 111.

In one or more embodiments, the sidewalls 182 of the spacer trough(s)181 can have an inside height above the trough surface 183 in the rangeof about 1 nm to about 5 nm, or in the range of about 2 nm to about 4nm.

FIG. 19 is a cross-sectional side view of the long axis of the verticalfins showing the spacer troughs on the end walls of the vertical fins,and the remaining portion of the gauge layer in the isolation regionbetween the vertical fins, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the gauge section(s) 191 can be removed, forexample, by a timed etch, to leave a portion of the gauge layer 190 inthe isolation trench to form the isolation region 195. The gaugesection(s) 191 can be removed down to the level of the trough surface183, so conductive gate material does not fill in spaces below the levelof a channel. The gauge section(s) 191 can be selectively etchedrelative to the exposed portions of the liner layer 170 and spacertrough(s) 181.

FIG. 20 is a cross-sectional side view showing removal of the exposedportions of the liner layer from each vertical fin and fin template, inaccordance with an embodiment of the present invention.

In one or more embodiments, the exposed portions of the liner layer 170can be removed to expose an upper portion of the vertical fin(s) 111 andfin template(s) 121, where the liner layer 170 can be removed using aselective etch. The portion of the liner layer 170 covered by thesidewalls 182 of the spacer trough(s) 181 can remain to form a U-shapedliner 171 between two vertical fins 111, or an L-shaped liner 171adjacent to a single vertical fin 111, where the liner is below theU-shaped spacer trough 181 or L-shaped spacer trough 181 respectively.In various embodiments, the combined liner layer 170 and spacer layer180 can form an L-shaped or U-shaped bottom trough on the end walls ofthe vertical fins 111. The liner layer 170 can be selectively etchedrelative to the material in the isolation region and spacer trough 181.

FIG. 21 is a cross-sectional side view showing a gate dielectric layerformed on the vertical fins, fin templates, and exposed surfaces of thespacer trough, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a gate dielectric layer 200 can be formed onthe exposed surfaces of the fin template(s) 121, vertical fin(s) 111,liners 171, and spacer trough(s) 181, where the gate dielectric layer200 can be conformally deposited by ALD, PEALD, CVD, PECVD, orcombinations thereof.

In one or more embodiments, the gate dielectric layer 200 can be aninsulating dielectric layer, for example, a silicon oxide (SiO), siliconnitride (SiN), silicon oxynitride (SiON), a high-K dielectric, or asuitable combination of these materials.

In various embodiments, the gate dielectric layer 200 can be a high-Kdielectric material that can include, but is not limited to, transitionmetal oxides such as hafnium oxide (e.g., HfO₂), hafnium silicon oxide(e.g., HfSiO₄), hafnium silicon oxynitride (Hf_(w)Si_(x)O_(y)N_(z)),lanthanum oxide (e.g., La₂O₃), lanthanum aluminum oxide (e.g., LaAlO₃),zirconium oxide (e.g., ZrO₂), zirconium silicon oxide (e.g., ZrSiO₄),zirconium silicon oxynitride (Zr_(w)Si_(x)O_(y)N_(z)), tantalum oxide(e.g., TaO₂, Ta₂O₅), titanium oxide (e.g., TiO₂), barium strontiumtitanium oxide (e.g., BaTiO₃—SrTiO₃), barium titanium oxide (e.g.,BaTiO₃), strontium titanium oxide (e.g., SrTiO₃), yttrium oxide (e.g.,Y₂O₃), aluminum oxide (e.g., Al₂O₃), lead scandium tantalum oxide(Pb(Sc_(x)Ta_(1-x))O₃), and lead zinc niobate (e.g.,PbZn_(1/3)Nb_(2/3)O₃). The high-k material can further include dopantssuch as lanthanum and/or aluminum. The stoichiometry of the high-Kcompounds can vary.

In one or more embodiments, the gate dielectric layer 200 can have athickness in the range of about 1 nm to about 4 nm, or can have athickness in the range of about 1 nm to about 2 nm.

FIG. 22 is a cross-sectional side view showing a work function layer onthe gate dielectric layer, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a work function layer 210 can be formed onthe exposed surfaces of the gate dielectric layer 200, where the workfunction layer 210 can be conformally deposited by ALD, PEALD, CVD,PECVD, or combinations thereof.

In one or more embodiments, a work function layer 210 can be formed onthe gate dielectric layer 200, where the work function layer 210 andgate dielectric layer 200 can surround at least a portion of each of oneor more vertical fin(s) 111 as a part of a gate structure. The workfunction layer 210 can be formed on the gate dielectric layer 200 toadjust the electrical properties of a gate electrode. In variousembodiments, the work function layer can be optional. A portion of thework function layer 210 can be formed on the gate dielectric layer 200on the spacer trough(s) 181 and liner(s) 171.

In various embodiments, a work function layer 210 can be a conductivenitride, including but not limited to titanium nitride (TiN), titaniumaluminum nitride (TiAlN), hafnium nitride (HfN), hafnium silicon nitride(HfSiN), tantalum nitride (TaN), tantalum silicon nitride (TaSiN),tungsten nitride (WN), molybdenum nitride (MoN), niobium nitride (NbN);a conductive carbide, including but not limited to titanium carbide(TiC), titanium aluminum carbide (TiAlC), tantalum carbide (TaC),hafnium carbide (HfC); or combinations thereof. The work function layer210 can include multiple layers of work function materials, for example,a work function layer can be a TiN/TiC stack.

In various embodiments, the work function layer 210 can have a thicknessin the range of about 1 nm to about 11 nm, or can have a thickness inthe range of about 1 nm to about 3 nm.

FIG. 23 is a cross-sectional side view showing a gate fill layer on thework function layer, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a gate fill layer 220 can be formed on thegate dielectric layer 200 and/or work function layer 210 if present,where the gate fill layer 220 can fill in the space between verticalfins 111. The gate fill layer 220, gate dielectric layer 200, andoptionally the work function layer 210, can form a gate structure on oneor more vertical fin(s) 111, where the gate fill layer 220 and workfunction layer 210 can form a conductive gate electrode.

In various embodiments, the gate fill layer 220 can be a p-doped polysilicon (p-Si), an n-doped poly silicon, a conductive metal, where themetal can be tungsten (W) or cobalt (Co), or a conductive carbonmaterial (e.g., carbon nanotube, graphene, etc.), or any suitablecombinations thereof. The gate fill layer 220 can be a heavily p-dopedpoly silicon to form a pFET, or a heavily n-doped poly silicon to forman nFET.

In one or more embodiments, the gate fill layer 220 can be blanketdeposited, and a chemical-mechanical polishing (CMP) used to remove gatefill layer material that extends above the top surfaces of the gatedielectric layer 200 and/or work function layer 210 if present, wherethe CMP can provide a smooth, flat surface.

FIG. 24 is a cross-sectional side view showing gate structures formed onthe vertical fins, and a top spacer formed on the exposed portions ofthe gate structure, in accordance with an embodiment of the presentinvention.

In one or more embodiments, the gate fill layer 220, gate dielectriclayer 200 and/or work function layer 210 if present, can be recessed toprovide space for formation of a top spacer layer 230. In variousembodiments, each of the gate fill layer 220, gate dielectric layer 200and/or work function layer 210 can be removed using a selective etch.The gate fill layer 220, gate dielectric layer 200 and/or work functionlayer 210 to a depth equal to or below the fin template(s) 121 toprovide space for formation of top source/drains on the top surfaces ofthe vertical fin(s) 111.

In one or more embodiments, the top spacer layer 230 can be the samematerial used for either the liner layer 170, the spacer layer 180, ormultiple layers thereof.

FIG. 25 is a cross-sectional side view showing top source/drains andsource/drain contacts on the top surface of each vertical fin, inaccordance with an embodiment of the present invention.

In one or more embodiments, an interlayer dielectric (ILD) layer 240 canbe formed on the exposed surface of the top spacer layer 230, where theinterlayer dielectric (ILD) layer 220 can be blanket deposited to fillin the spaces between the vertical fins 111 and/or fin templates 121.

In one or more embodiments, the ILD layer 240 can be silicon oxide(SiO), a low-k dielectric, a flowable polymeric material, or acombination thereof. A low-k dielelctric material can include, but notbe limited to, a fluoride-doped silicon oxide (e.g., fluoride dopedglass), a carbon doped silicon oxide, a porous silicon oxide, a spin-onsilicon based polymeric material (e.g., hydrogen silsesquioxane (HSQ)and methylsilsesquioxane (MSQ)), or combinations thereof. In variousembodiments, the ILD layer 220 can be formed by CVD or spun on.

In one or more embodiments, the height of the ILD layer 220 can bereduced using CMP to expose the top surfaces of the gate dielectriclayer 200 or work function layer 210. A selective etch can be used toremove the exposed portions of the gate dielectric layer 200 and workfunction layer 210 to expose the underlying fin template 121. The fintemplate 121 can be removed to expose the top surface of the underlyingvertical fin 111, where the top surface 113 of the vertical fin 111 canhave a crystalline face.

In one or more embodiments, a top source/drain 250 can be formed on eachof the vertical fin(s) 111, where the top source/drains 250 can beepitaxially grown on the crystalline top surfaces 113.

In one or more embodiments, the metal electrode(s) 260 can be formed inthe ILD layer 240 to provide conductive electrical paths to each of thetop source/drains 250 and vertical fins 111 to form a vertical transportFinFET with wrap-around gate structures and U-shaped or L-shaped bottomspacers including liners 171 and spacer troughs 181. Bottom contacts tobottom source/drains can be fabricated at the same time as the metalelectrode(s) 260 forming the electrical contacts to the topsource/drains 250.

FIG. 26 is a cross-sectional side view of the long axis of the verticalfins showing the vertical fins, gate structures, source/drains, andelectrical contacts for an nFET and an adjacent pFET, in accordance withan embodiment of the present invention.

In one or more embodiments, a portion of the bottom trough, gatestructure, and ILD layer 240 can be removed to form a bottomsource/drain contact 290 to the bottom source/drain region(s) 115. Theportions of the bottom trough, gate structure, and ILD layer 240 can beremoved by a series of selective masking and etching processes to exposethe underlying bottom source/drain region(s) 115. A contact region liner270 can be formed on the bottom source/drain region(s) 115 and verticalsides of the gate structure(s) and ILD layer 240 to electrically isolatethe conductive gate material (i.e., the gate electrode). A second ILDlayer 280 can be formed on the contact region liner 270, and a trench orvia can be formed in the second ILD layer 280 and contact region liner270 to expose at least a portion of the bottom source/drain region 115.Bottom source/drain contacts(s) 290 can be formed in the ILD layer 280to provide conductive electrical paths to each of the bottomsource/drain regions 115. The bottom source/drain contacts(s) 290 andmetal electrode(s) 260 can be formed at the same time using the samedeposition.

A bottom source/drain region 115 and extension region 116 can form abottom source/drain.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or including, when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or ore other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein can be interpreted accordingly. In addition, itwill also be understood that when a layer is referred to as being“between” two layers, it can be the only layer between the two layers,or one or more intervening layers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

Having described preferred embodiments of a device and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A method of forming a vertical transport finfield effect transistor, comprising: forming one or more vertical finson a substrate; forming an extension region at the base of at least oneof the one or more vertical fins; forming a spacer layer on thesubstrate and exposed surfaces of the one or more vertical fins; forminga gauge layer on the spacer layer; removing a portion of the gauge layerto form one or more gauge sections on the spacer layer, wherein aportion of the spacer layer on the one or more vertical fins is exposedby removing the portion of the gauge layer; and removing the exposedportion of the spacer layer to form an L-shaped or U-shaped spacertrough.
 2. The method of forming a vertical transport fin field effecttransistor of claim 1, further comprising, forming a liner layer betweenthe substrate and the spacer layer and between the one or more verticalfins and the spacer layer, and removing a portion of the liner layer onthe one or more vertical fins exposed by removing the exposed portion ofthe spacer layer.
 3. The method of forming a vertical transport finfield effect transistor of claim 1, further comprising, removing the oneor more gauge sections to expose an inside sidewall of the L-shaped orU-shaped spacer trough.
 4. The method of forming a vertical transportfin field effect transistor of claim 3, further comprising, forming agate dielectric layer on the exposed portion of the one or more verticalfins and inside sidewall of the L-shaped or U-shaped spacer trough. 5.The method of forming a vertical transport fin field effect transistorof claim 4, wherein the material of the L-shaped or U-shaped spacertrough is silicon nitride (SiN), and wherein the inside sidewall has aheight above the trough surface in the range of about 1 nm to about 5nm.
 6. The method of forming a vertical transport fin field effecttransistor of claim 4, further comprising, forming a top source/drain onthe top surface of the at least one of the one or more vertical fins,and a bottom source/drain below the at least one of the one or morevertical fins.
 7. The method of forming a vertical transport fin fieldeffect transistor of claim 6, further comprising, forming a workfunction layer on the exposed surfaces of the gate dielectric layer, andforming a gate fill layer on the work function layer.
 8. The method offorming a vertical transport fin field effect transistor of claim 7,wherein the gate fill layer is above the L-shaped or U-shaped spacertrough.
 9. The method of forming a vertical transport fin field effecttransistor of claim 8, further comprising forming a contact region lineron a portion of the gate fill layer.